1. Field of the Invention
The invention relates to a system for localizing an object in a turbid medium. The invention also relates to a method for localizing an object in a turbid medium.
Such a system is advantageously used for imaging human or animal tissue. In particular, in the field of mammography detection of an object in a turbid medium is employed to detect a tumour in a woman's breast.
2. Description of the Related Art
Such a system is known from the article Highly sensitive object location in tissue models with linear in-phase and anti-phase multi-element optical arrays in one and two dimensions, by B. Chance et al. in the Proceedings of the National Academy of Science USA Vol. 90 (1993) 3423-3427.
The known system comprises spatially separated light sources emitting substantially the same wavelength. The light sources are amplitude modulated with essentially the same frequency and with a phase difference of about 180.degree.. When the known system would illuminate a homogeneous medium the amplitude modulations cancel along the perpendicular bisector of the separation of the two sources. Any inhomogeneity like an object in the turbid medium causes a deviation from the cancellation of the Amplitude modulation along the perpendicular bisector and as a consequence a signal is detected by a photodetector set-up on the perpendicular bisector. However, the known system does not provide information pertaining to the composition of the object. Hence, the known system is e.g. unable to distinguish a malignant cancerous tumour from a benign tumour.